Digital single-lens reflex cameras in which exchangeable imaging lenses can be attached to a main body unit have been marketed as camera systems (imaging systems) in recent years. High-sensitivity imaging with less blurring or noise can be achieved by selecting a desired type from among imaging lenses with various angles of view and brightnesses, and attaching the selected lens to the main body unit.
Generally, available combinations of the main body unit and the imaging lens are often limited for digital single-lens reflex cameras. As a countermeasure, an imaging device, an image processor, and the like are installed in the imaging lens to generate image data on the imaging-lens unit side and transmit the data to the main body unit. This allows a wider variation of imaging lenses to be used in combination with the main body unit.
Further, by generating object image data in an interchangeable lens unit equipped with an imaging device and processing the image data in the main body unit connected to the lens unit, units of the imaging system can be made smaller and image data processing speed can be improved. In addition, by recording image data of a large data amount in a storage of the lens unit and transferring image data downsized through pixel skipping to the main body unit as disclosed in JP2007-110314A, power consumption for data transfer can be suppressed, so that a more energy-efficient device can be achieved.
Such a configuration makes it possible to smoothly attach various replacement lenses to a main body of a camera and utilize a higher performance. In this case, however, each of the units is to install firmware including multiple functions, which causes an important problem of compatibility among the firmwares of the units. Firmware versions may differ among units of the same model, though the difference is difficult to tell from outside. Hence, a lens unit is often attached to a main body unit without checking, and as a result does not operate because of the difference in the firmware version.
For this reason, it is necessary in this type of camera system to make compatible the firmware versions of the image processor on the lens unit side and the image processor on the main body unit side.
JP2006-121418A discloses a technique in which the firmware version of the lens unit is upgraded with firmware transmitted from the main body unit. At the time of upgrading the firmware version of the lens unit, a version number of the firmware is checked so that a warning may be displayed if the firmware version of the lens unit will be downgraded, and version update processing may be performed automatically if the firmware version of the lens unit will be upgraded.
JP2007-266780A discloses a configuration in which information on the firmware version of each component is displayed to the user so that the user can manage them and keep them up to date. The configuration also makes it possible to automatically upgrade the firmware versions of the components if upgrading is necessary.
JP2008-116660A discloses a similar configuration which allows management of version information on each component and automatic upgrading if necessary. Additionally, this configuration makes it possible to update the firmware to the latest version by downloading it from a server.
However, assume a case where the main body unit is of an old version and upgrading only the lens unit will disable normal operation of the system as a whole. With the version update processing configured in the aforementioned manner, the lens unit could be upgraded erroneously, so that in the worst case, it may become impossible to start up the camera system. In addition, there are problems that the lens unit and the main body unit have separate firmwares and that there are constraints such as compatibility among the different versions thereof, so that it is bothersome to manage the versions. Moreover, to adjust the camera to an optimal imaging condition or the like by taking advantage of the interchangeable lenses, a wider variation of lens units needs to be used, which makes the aforementioned problem even larger.